In some networks, such as Multiprotocol Label Switching (MPLS) networks and Generalized MPLS (GMPLS) networks, a Traffic Engineering (TE) Label Switched Path (LSP) can be established using a Resource Reservation Protocol-TE (RSVP-TE) for a given path. A path can be provided by a Path Computation Client (PCC) and/or a Path Computation Element (PCE). For example, the PCC may request a path or route from the PCE, which computes the path and forwards the computed path information back to the PCC. The path can be a point-to-point (P2P) path, which comprises a plurality of nodes and/or Label Switch Routers (LSRs) and extends from a source node or LSR to a destination node or LSR. Alternatively, the path can be a Point-to-Multipoint (P2MP) path that extends from the source node to a plurality of destination nodes. The RSVP-TE can also be used to establish backup P2P and P2MP LSPs to reroute packets during network link or internal node failures and thus guarantee packet delivery.
The Internet Engineering Task Force (IETF) Request for Comments (RFC) 4655 entitled “A Path Computation Element (PCE)-Based Architecture”, which is incorporated herein by reference, describes a set of building blocks for constructing solutions to compute a path for a P2P TE LSP across multiple areas or Autonomous System (AS) domains. A typical PCE-based system comprises one or more path computation servers, traffic engineering databases (TED), and a number of PCCs. The routing protocol is used to exchange traffic engineering information from which the TED is constructed. A PCC sends a path computation request for a P2P TE LSP to the path computation server, which uses the TED to compute the path and responds to the PCC with the computed path. A path computation server may be referred to as a PCE, or a PCE may be an application running on a server. The communications between a PCE and a PCC for P2P LSP path computations follow the PCE communication protocol (PCEP).
The IETF RFC 4875 entitled “Extensions to Resource Reservation Protocol—Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths”, which is incorporated herein by reference, describes a mechanism for setting up P2MP traffic engineering label switched paths. A P2MP LSP is comprised of multiple Source-to-Leaf (S2L) sub-LSPs. These S2L sub-LSPs are set up between the ingress and egress LSRs and are appropriately combined by the branch LSRs using Resource Reservation Protocol (RSVP) semantics to result in a P2MP TE LSP.
The IETF RFC 6006 entitled “Extensions to the Path Computation Element Communication Protocol (PCEP) for Point-to-Multipoint Traffic Engineering Label Switched Paths”, which is incorporated herein by reference, describes extensions to the PCEP to handle requests and responses for the computation of a path for a P2MP TE LSP crossing multiple domains. A mechanism for a PCC to send a request for computing a backup ingress for a P2MP LSP to a PCE and for a PCE to reply to the PCC with a computation result for the backup ingress is described in U.S. patent application Ser. No. 13/033,125 filed Feb. 23, 2011 by Huaimo Chen and entitled “System and Method for Computing a Backup Ingress of a Point-to-Multipoint Label Switched Path”, which is incorporated herein by reference as if reproduced in its entirety.
However, no procedure for finding a backup ingress of a P2MP TE LSP and a backup path from the backup ingress to the next-hop nodes of the ingress node of the LSP is described in any of the documents mentioned above. There is thus a need for efficient procedures for finding a backup ingress for a P2MP TE LSP, a backup path from the backup ingress to the next-hop nodes of the ingress node of the LSP, and a path from a source node to the backup ingress node.